papaya
Class Normality

java.lang.Object
  extended by papaya.Normality
All Implemented Interfaces:
PapayaConstants

public class Normality
extends Object
implements PapayaConstants

Contains various utilities for checking if the dataset comes from a normal distribution.


Nested Class Summary
static class Normality.Dago
          Methods for computing the skewnewss, kurtosis, and D'Agostino-Peasrson K^2 "omnibus" test-statistics (that combine the former two), and accompanying significance (or p-values) for testing the underlying population normality.
 
Field Summary
 
Fields inherited from interface papaya.PapayaConstants
BASELINE, big, biginv, BOTTOM, CENTER, CORNER, FONTNAME, GRAY, INDEX_NOT_FOUND, INDICES_NOT_FOUND, LEFT, LOGPI, MACHEP, MAXGAM, MAXLOG, MINLOG, RIGHT, SQRTH, SQTPI, STROKEWEIGHT, TEXTSIZE, TOP
 
Method Summary
static float[] normalProbability(float[] data)
          Return the Normal order statistic medians (N) necessary to produce a Q-Q plot for a normal distribution (or normal probability plot).
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Method Detail

normalProbability

public static float[] normalProbability(float[] data)
Return the Normal order statistic medians (N) necessary to produce a Q-Q plot for a normal distribution (or normal probability plot). That is, given a data array, this method computes the Normal order statistic medians and the ordered response values or z-scores of the input. A plot of the N vs z should form an approximate straight line if the data is normally distributed; departures from this straight line indicate departures from normality with the shape of the line providing clues as to the distribution of the data.

The normal order statistic medians are computed as
N[i] = Probability.norminv(U[i]) where U[i] are the uniform order statistic medians, given by

Reference: NIST/SEMATECH e-Handbook of Statistical Methods, EDA Section 1.3.3.21: Normal Probability Plots

Parameters:
data - the data array
Returns:
the Normal order statistic medians
See Also:
Descriptive.zScore(float[],float,float)


Processing library papaya by Adila Faruk. (C) 2014